For investigations in this proposal, expert lymphoma diagnostic skills, immunophenotypic and molecular capabilities, and well-characterized tissue are imperative. Members of the Pathology Core (Core B) will provide the following functions: (1) Pathology Review: Acurate diagnosis of lymphomas will be provided by experienced hematopathologists and molecular pathologists. (2) Tissue banking and distribution: A large number of patient samples are stored, catalogued, and readily retrievable for use in the proposed investigations. The Pathologists will provide selection of appropriate material for the proposed studies from over 15,500 tissue specimens available in our archive. (3) Tissue microarrays (TMA): TMAs are an efficient method for studying protein expression, enabling rapid survey of hundreds of patient samples in a single experiment. TMAs will be used for protein expression studies of newly characterized monoclonal antibodies and novel markers identified by gene expression studies in lymphomas. TMAs will also be used to archive patient samples on an on-going manner as they are accrued into clinical studies described in this proposal. (4) Characterization of new antibodies and testing prognostic models by immunohistochemistry (IHC): IHC with a variety of antibodies with sophisticated methods for their analysis will be provided by members of the Pathology Core. Newly generated antibodies to targets identified by gene expression studies will be characterized using TMAs and IHC techniques.